Chapter 6: Ionic and Molecular Compounds

Metals and Nonmetals

• Metals are elements that tend to lose electrons during chemical reactions, forming positively charged ions called cations.

• Nonmetals are elements that tend to gain electrons, forming negatively charged ions called anions.

• Nonmetals can also share electrons with other nonmetals to form covalent bonds.

Ionic and Covalent Bonds

• Ionic bond: Formed between a cation (from a metal) and an anion (from a nonmetal).

• Covalent bond: Formed when nonmetals share electrons (no charge transfer).

Octet Rule

• Atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight valence electrons (like noble gases).

Predicting Ion Charges

• The charge of main group metals and nonmetals can be predicted based on their position in the periodic table.

• Group 1 metals: +1; Group 2 metals: +2; Group 17 nonmetals: -1; Group 16 nonmetals: -2, etc.

Naming and Writing Formulas for Ionic Compounds

• To write formulas from names: Identify the ions and their charges, then combine them in the smallest ratio that results in a neutral compound.

• To write names from formulas: Name the cation first, then the anion. For transition metals, indicate the charge with Roman numerals.

Monoatomic and Polyatomic Ions

• Monoatomic ions: Ions formed from single atoms (e.g., Na+, Cl-).

• Polyatomic ions: Ions composed of two or more atoms covalently bonded, carrying a charge (e.g., NO3-, SO42-).

Naming and Writing Formulas for Molecular Compounds

• Use prefixes to indicate the number of each atom: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-.

• These prefixes are not used for ionic compounds.

• Write the formula based on the prefixes in the name.

Molecular Elements

• Some elements exist naturally as diatomic molecules: H2, N2, O2, F2, Cl2, Br2, I2.

Lewis Structures and Molecular Shapes

• Lewis structures show the arrangement of valence electrons around atoms in a molecule.

• Bond pairs are shared electrons; lone pairs are unshared electrons.

• The shape of a molecule can be deduced from its Lewis structure (e.g., linear, bent, trigonal planar, tetrahedral).

Electronegativity and Bond Polarity

• Electronegativity is the ability of an atom to attract shared electrons in a bond.

• A difference in electronegativity between atoms leads to polar bonds.

Hydrogen Bonding

• Hydrogen bonds occur when hydrogen is bonded to N, O, or F, leading to strong intermolecular attractions.

Chapter 7.3: Balancing Chemical Reactions

Principles of Balancing Chemical Equations

• Never change the subscripts in chemical formulas when balancing equations.

• Only change the coefficients (the numbers in front of compounds or elements).

• Always check that the number of atoms of each element is the same on both sides of the equation.

• Treat polyatomic ions as a group if they appear unchanged on both sides.

Example Equation

• Unbalanced:

• Balanced:

Chapter 8: Gases

Properties of Gases

• Gases have no fixed shape or volume and are easily compressible.

• Common units for gas properties include:

  • Pressure: atm, mmHg, torr, kPa

  • Volume: L (liters), mL (milliliters)

  • Temperature: K (Kelvin), °C (Celsius)

Pressure Units and Conversions

• 1 atm = 760 mmHg = 760 torr = 101.3 kPa

Boyle's Law

• Describes the inverse relationship between pressure and volume at constant temperature.

Dalton's Law of Partial Pressures

• The total pressure of a mixture of gases is the sum of the partial pressures of each gas.

Chapter 9: Solutions

Components of a Solution

• A solution is a homogeneous mixture of a solute (substance being dissolved) and a solvent (substance doing the dissolving).

Solubility Principles

• Like dissolves like:

  • Polar solutes dissolve in polar solvents.

  • Nonpolar solutes dissolve in nonpolar solvents.

  • Water is a polar solvent and dissolves only polar solutes.

Electrolytes and Nonelectrolytes

• Electrolytes: Substances (ionic compounds and acids) that dissociate into ions in water and conduct electricity.

• Nonelectrolytes: Molecular compounds that do not conduct electricity in water.

Solubility and Saturation

• Solubility is usually expressed as grams of solute per 100 grams of water.

• A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

• An unsaturated solution can dissolve more solute.

Effect of Temperature and Pressure on Solubility

• For solids and liquids, solubility increases with increasing temperature.

• For gases, solubility decreases with increasing temperature but increases with increasing pressure.

Solution Concentration

• Common ways to express concentration:

  • Mass percent:

  • Volume percent:

  • Mass/volume percent:

• If two of the following are known—amount of solute, amount of solvent, concentration—you can calculate the third.

Solution Dilution

• To dilute a solution, use the formula:

• Where C1 and V1 are the initial concentration and volume, and C2 and V2 are the final concentration and volume.